The present invention relates to processes for removing one or more metals from tallow oils. More particularly, the invention relates to such processes using an ionic liquid.
Tallow oil is a rendered form of fat, mainly from beef or mutton, although industrially, tallow oil may include fat from other animals such as pigs. Tallow manufacture consists of freeing fat from its associated tissues by heat rendering and then refining it to separate it from the solids and water which would lead to its deterioration. Tallow oil (also known as “tallow”) is used in animal feed, to make soap, shoe polish, for cooking and as a bird food. It can be used as a raw material for the production of biodiesel and other chemicals. Tallow also has a history of use as a lubricant for machinery as well as for ammunition. In addition to fat, tallow typically contains parts per million levels of a variety of minerals or metals. In one particular study, the level of such minerals was found to range from about 10-20 ppm sodium, 2-3 ppm potassium, 1-2 ppm calcium, 0.4-0.5 ppm iron, 1.1-1.2 ppm lead, 0.4 to 0.5 ppm magnesium, 0.070 ppm cadmium, 0.025 to 0.055 ppm zinc, 0.8 to 1.0 ppm chromium. Ali, Pakistan JOURNAL OF NUTRITION 7 (5) 717-720, 2008. Analysis of 3A Darling animal fat, a type of tallow is shown in the table below.
Tallow3A Darling Animal FatAPI23.23Specific Gravity, 60° F.0.9145Hydrogen, wt-%12.01Carbon Residue, wt-%0.62Al, wt-ppm2.4Ca, wt-ppm3.63Fe, wt-ppm5.5Na, wt-ppm300P, wt-ppm32K, wt-ppm14.6Nitrogen, wt-ppm1736Sulfur, wt-ppm421Water, wt-ppm2210
Processes have been recently developed which take vegetable oils, or lipids, and convert them into replacements for diesel and jet fuels, recent filings include the following references: US2009283442, US2009301930, US2009287029, US2009253947, US2009250376, US2009294324, US2009162264, and US2009158637.
The resultant fuels from this refining process are indistinguishable from existing fossil based petro-diesels and jet fuels. In addition to vegetable oils, tallow is one source of fat that is suitable for converting into a diesel or jet fuel. Tallow contains metal contaminants and in particular, contains ppm levels of iron which acts as a catalyst poison. It is thought that the iron contaminant is in the form of the heme molecule from traces of blood in the tallow. The heme molecule contains iron that is at the center of a nitrogen ring structure within a hydrocarbon molecule. This invention uses specific ionic liquids to extract iron from tallow.
The prior art includes Liquid/Liquid Extraction of Metal Ions in Room Temperature Ionic Liquids, by Visser, Ann E., et al, SEPARATION SCIENCE AND TECHNOLOGY, 36(5&6), 785-804, (2001), Marcel Dekker, Inc., discloses the use of room temperature ionic liquids, specifically, 1-alkyl-3-methylimidazolium hexafluorophosphate, to separate metal ions from aqueous solutions. However, there remains a need in the art for improved processes that reduce the metal content of tallow.